1. Field of the Invention
The present invention relates the dynamic reduction of telephone call congestion, and more particularly, to the dynamic reduction of telephone call congestion in a mobile telephone system.
2. Description of the Related Art
In a mobile telephone communication system, such as the global system for mobiles (GSM) telephone communication system, "call setup" occurs over common control channels. As illustrated in the mobile telephone communication system 10 of FIG. 1, a mobile telephone unit 12 is located in one of cell clusters 14, 16, and 18, each of which includes cells A-G. The mobile telephone unit 12 measures the power level of a number of base stations 20, 22, and 24 in the general vicinity, and reports the power level measurements to a base station controller 26 via the respective base stations 20, 22, 24. The base station controller 26 then sets up or assigns a call requested by the mobile terminal unit 12 on the strongest base station 20, 22, 24. The base station controller 26 makes the decision for the mobile terminal unit 12 and sends an order to the strongest serving base station 20, 22, 24 (as reported by the mobile terminal unit 12) to set up the desired call.
Congestion occurs when too many mobile terminal units are trying to set up calls on a particular cell, (in this case, cell A in cell cluster 16) which requires additional channel capacity above its existing configuration.
The cluster of cells 16 provides service to the mobile terminal units 12 within their coverage area. In some cases, mobile users may gather with much higher density around one cell in a cluster 16, causing a much higher blocking probability for that cell, than is present in the neighboring cells.
In a particular example, cell A of cell cluster 16 includes an area in which an event, such as a sporting event, is taking place and cell A experiencing congestion levels in excess of a threshold, for example 10% of the calls are not being assigned, whereas the congestion of all other cells B-G in cluster 16 is much less than 10%, for example less than 1%. This congestion prevents some of the mobile telephone units within cell A of cluster 16 from having their calls assigned. As a result, many subscribers are unable to complete their desired calls.